Method of manufacturing finely-divided carbon and by-products from coal-pitch.



ARCHIBALD EVANS, 01E HAMPTON WICK, AND PERCY JOSE MITCHELL, OF

WESTMINSTER, LONDON, ENGLAND.

METHOD OF MANUFACTURING FINELY DIVIDED CARBON AND BY-PRODUCIS FROM COAIi-PITG'H.

1,175 732. I Specification of Letters latent. Patented M 141916 No Drawing. Application fi led December 22,1915. Serial No. 68,248.

' To all whom it may concern:

- it appertains to make and use Be it known that we, ABCHIBALD CLAUDE EVANS and PERCY J o'sE MITCHELL, residing at Lucerne House, Hampton Wick, Midd lesex, England, and Caxton House, Westmlnster, London, S. W., England, respectively, have invented certain new and useful Improvements in the Method of Manufacturing Finely-Divided Carbon and By-Products from Coal-Pitch; and we do hereby declare the following to be a full, clear, exact description of the invention, such as will enable others skilled in the art to which the same.

This invention relates to an improved method for the manufacture of carbon powder, that is to say, a finely comminuted material which is allied to lamp .black but which by reason of its manufacture cannot be technically described as suc Heretofore in treating coal pitch-for the manufacture of carbon powder by means of naphtha it has not been possible to employ the same naphtha over and over again without purification because of the presence of phenols and sulfur compounds which as a by the previous treatment of the coal pitch out above,

' of about 100 degrees centigrade with an alkaline solution. Moreover by avoiding a complete removal of said prior alkaline washings as a further feature of the invention a frothing necessarily occurs which offers considerable advantage when the Y introduction of the naphtha is made.

Having the'objects of our invention are to provide a convenient and economical process for the production of carbon powder and valuable by-products' from pitch.

A further object of our invention is to provide a process for obtaining the products above mentioned in which the solvent may be employed over and over again without purification.

Theinvention is carried out as follows Crude coal pitch is heated to a temperature in a closed still or other suitable vessel. It is then mixed with a weak solution of caustic soda, caustic potash or other suitable basic oxids or hydroxids and agitated for the purpose of removing the phenols and any sulfur and in mind the state of facts as set compounds that may be present. The alkahne solution used is preferably of about one-eighth per cent. strength, and the amount used per'charge of pitch is equal by weight to that of the pitch. The mixture is then allowed to stand, when the aqueous facilities the process of siphoning. It is important that a certain amount of moisture or aqueous solution should be left in the pitch for reasons-which will be described hereafter.

The next stage of the process is to dissolve. out the oils and other constituents of the pitch and leave the free carbon behind. For this purpose ordinary commercial .solvent naphtha is used. The treatment with naphthais preferably carried out in the same vessel as that which is used for the alkali treatment. A quantity of naphtha equal to three times the weight of the pitch used is added to the latter which is warmed to a temperature of 100 centigrade, and

agitated, the said temperature be;

violently ing malntained throughout the operation.- In order to facilitate the solvent action of the naphtha it is important that the pitch on being heated into-a large number of small particles, and

.this end is best achieved by allowing a certain amount of water to remain in the pitch from the previously described alkaline should froth or separate I washing. The amount of moisture necessag for this purpose is not large but it is di cult to state a definite quantity; the same canhowever be easily determined by a trial experiment. ignored it will be found that the pitch will have a tendency to ball or' separate into lumps, and' the-solvent action of the naphtha will thus be greatly impeded, the comquiring considerably longer time and heating than is the case if the precaution re- If this precaution be 10c pletion of this part of the process thus referred to above is taken. By these means a fairly thick solution is obtained, and to this a second portion of. solvent is added cold, the contents of the still being kept at 100 centigrade and agitated for a few minutes. This second portion of naphtha may be either once or twice the amount in weight of the pitch used according as it'is-desired to, obtain perfectly pure carbon or carbon containing a small amount of bitumen..

ing carried out under atmospheric pressure. a

The mixture is now allowed to stand, when the carbon, or most of it, will settle to the bottom as a sludge, while the li uid will separate intoone or more layers w ich can be run off or decanted. by suitable drawofi cocks, siphons or other suitable means. If desired a filter press may be used at any stage after this second naphtha treatment in order to accelerate the separation of the carbon. a a

The carbon is obtained in a finely divided but usually rather crude state, and it will generally require re-washing with naphtha, in which case the settling, filtration and decantation processes may be repeated as before. As regard the quantities of naphtha used for this and the other washings referred to, it should be stated that excepting in the case in which the highest degree of purity. in the carbon may be required, the total amount of naphtha used in the process need not exceed six times the weight of pitch. Ashas been stated, three times the weight of pitch in naphtha are used for the first treatment, once or twice the weight of pitch is used for the second treatment,

and the amount used for this final washing is regulated by the amount'previously used in such a way that the total weight used does not exceed six times that of the pitch. After final decantation of the liquids or separation therefrom of the carbon by any suitable means the latter is dried in a closed vessel and heated to drive ofi' any volatile residues which may if desired be collected by suitable condensers. The carbon is thus obtained in a finely divided caked condition, and it may then be removed from the vessel, disintegrated or ground in any suitable appliance, and finely pulverized pure carbon obtaine As regards the quantities ofnaphtha usedin the processes,'.it, should-be stated that six times. the .weight of pitch in naphtha will suflice to produce what maybe regarded as a fairly pure carbon. For certain purposes it has been found desirable for the carbon to contain a small quantity of bitumen-thus facilitating the molding of the powder into any desired shape, and the quantity of bitumen left in the product may and any desired number of washings with naphtha may be imparted to the carbon without departing fromthe spirit of the invention.

After the naphtha washings have been freed, either by settling and decantation, or by the use of a filter press, from all traces .of' free carbon, they are distilled for the purpose of recovering the solvent oils and other substances held in solution. In this recovery process any convenient method of fractional distillation may be used and the .process will yield, firstly, the solvent, secondly any intermediate oils contained in the pitch and thirdly a pitch absolutely free from all acid substances and from all free carbon. If necessary the products obtained in the recovery process, both solvent and oils, can be re-distilled for the purpose of purification, and any convenient known type vof fractionating column or the like can be used for such purification.

It will thus be seen that this process yields at will either an absolutely pure carbon in a finely divided state or a carbon containing a small quantity of bitumen which renders it suitable for certain special purposes, and in addition that valuable byproducts from the pitch are recovered. Apart from the working losses which cannot be avoided in any manufacturing process there is no loss of solvent, which latter can be used over and over again, and similarly the phenols and sulfur compounds removed in the preliminary alkaline treatment may if desired be recovered by any suitable means while the alkaline solution may be used for a number of charges of pitch without being renewed.

' We claim 1. Amethod of manufacturing finely divided carbon consisting in first treating coal pitch. in a hot condition with a weak alkaline solution, substantially removing the washings and subsequently digesting the mass with solvent naphtha, then separating vided carbon consisting in first treating coal pitch in a hot condition with a Weak alkaline solutlon, substantially removing the washings from the pitch but leaving a small quantity of moisture or alkaline solution rating the free carbon, and distilling the retherein, heating the mass to cause frothing, maining liquid for a by-product. digesting the mass with solvent naphtha, In testimony whereof we aflix our signaand tlAien separatifng theffree carbofln. '1 d1 tures in presence of twowitnesses. 5 3. i method 0 manu acturing ne y vided carbon and by-products consisting in g first treating coal pltch in a hot condition with a weak alkaline solution, substantially Witnesses:

removing the washings and subsequently di- FRANK B. DEHM, 10 gesting the mass with solvent naphtha, sepa- I H. C. WESTON. 

